The effects of feeding rations that differ in neutral detergent fiber and starch within a day on the daily pattern of key rumen microbial populations.

The effect of feeding a single TMR versus multiple rations across the day that differ in concentrations of neutral detergent fiber (NDF) and starch on the daily pattern of rumen microbial populations was characterized. Diets included a control total mixed ration (CON; 33.3% NDF), a low-fiber diet (LF; 29.6% NDF), and a high-fiber diet (HF; 34.8% NDF). Nine cannulated Holstein cows were assigned to 1 of 3 treatment sequences in a 3 × 3 Latin square design. Treatments included feeding CON ad libitum at 0900 h, feeding HF at 70% of daily offering at 0900 h and LF at 30% of daily offering at 2200 h (H/L), and feeding LF at 30% of daily offering at 0900 h and HF at 70% of daily offering at 1300 h (L/H). Rumen digesta was collected to represent every 3 h across the day, microbial DNA was extracted, and real-time quantitative PCR was used to determine the relative abundances of total bacteria, total fungi, total protozoa, Butyrivibrio fibrisolvens, Butyrivibrio hungatei, Fibrobacter succinogenes, Megasphaera elsdenii, Prevotella bryantii, Ruminococcus albus, Selenomonas ruminantium, and Streptococcus bovis. The relative abundances of total bacteria, total ciliated protozoa, F. succinogenes, P. bryantii, R. albus, S. ruminantium, and Strep. bovis were affected by time of day. Additionally, treatment affected the relative abundance of certain microbial groups at specific times of day. Notably, H/L treatment dramatically increased the relative abundances of B. fibrisolvens, B. hungatei, and Strep. bovis at 0900 h, by 2.5-, 5.4-, and 4.4-fold, respectively. Furthermore, the relative abundances of B. hungatei (3.9-fold), M. elsdenii (3.9-fold), R. albus (1.3-fold), S. ruminantium (1.3-fold), and Strep. bovis (4.5-fold) were greatly increased by L/H at 0900 h. At 0600 h, the relative abundance of F. succinogenes was 58% greater in L/H than H/L and the relative abundance of P. bryantii was 49% greater in H/L than L/H. Results suggest that there is a daily pattern of selected microbial populations that is altered by feeding rations that differ in NDF and starch within a day, with the greatest difference occurring before morning feeding.

The effects of feeding rations that differ in neutral detergent fiber and starch concentration within a day on rumen digesta nutrient concentration, pH, and fermentation products in dairy cows.

There is a daily pattern of feed intake in the dairy cow, and feeding a single total mixed ration results in variation in the amount of fermentable substrate entering the rumen over the day. The object of this study was to determine if feeding multiple rations over the day that complement the pattern of feed intake would stabilize rumen pool sizes and fermentation. Nine ruminally cannulated cows were used in a 3×3 Latin square design with 23-d periods. Diets were a control diet [33.3% neutral detergent fiber (NDF)], a low-fiber diet (LF; 29.6% NDF), and a high-fiber diet (HF; 34.8% NDF). The LF and HF diets were balanced to provide the same nutrient composition as the control diet when cows were fed 3 parts of LF and 7 parts of HF. Cows on the control treatment (CON) were fed at 0900h, cows on the high/low treatment (H/L) were fed HF at 70% of daily offering at 0900h and LF at 30% of daily offering at 2200h, and cows on the low/high (L/H) treatment were fed LF at 30% of daily offering at 0900h and HF at 70% of daily offering at 1300h. All treatments were fed at 110% of daily intake. Preplanned contrasts compared CON with H/L and H/L with L/H. Feeding the LF diet in the evening resulted in a large increase in the amount of feed consumed immediately after feed delivery at that feeding. Rumen digesta starch concentration increased and NDF concentration decreased following feeding of the LF diet in both the L/H and H/L treatments. Starch pool size also increased following feeding of the LF diet in the evening and tended to increase after feeding the LF diet in the morning. Rumen ammonia concentration was increased following feeding of the HF diet in the morning and the LF diet in the evening in the H/L treatment. Additionally, cis-9 C18:1 and cis-9,cis-12 18:2 are higher in concentrate feeds and were increased after feeding the LF diet in both treatments. Trans fatty acid isomers of the normal and alternate biohydrogenation pathways followed a daily pattern, and the H/L treatment increased isomers of the alternate pathway during the overnight period following the evening feeding of the LF diet. Additionally, C17:0 decreased during the overnight period in the H/L treatment. Feeding multiple rations over the day changed feeding behavior, and the combined effect of diet composition and feeding pattern resulted in a change in rumen nutrient pool sizes and fermentation products. Feeding the low-fiber diet in the evening resulted in a large increase in feed intake after feed delivery and did not increase starch intake during the overnight period. The H/L treatment failed to stabilize rumen fermentation because of the shift in the feeding pattern. Feeding strategies that feed multiple diets over the day must integrate diet composition and feeding behavior to achieve the desired effect on rumen nutrient pools and fermentation.

The effects of feeding rations that differ in neutral detergent fiber and starch concentration within a day on production, feeding behavior, total-tract digestibility, and plasma metabolites and hormones in dairy cows.

Dairy cows exhibit a daily pattern of feed intake and milk synthesis, and feeding a single total mixed ration over the day may not synchronize ruminal fermentation, nutrient absorption, and milk synthesis. Our hypothesis was that feeding a high-fiber diet during the high-intake period of the day and a low-fiber diet during the low-intake overnight period would stabilize rumen fermentation, nutrient absorption, and the availability of nutrients for milk synthesis. Nine ruminally cannulated cows were used in a 3×3 Latin square design with 23-d periods. Diets were a control [CON; 33.3% neutral detergent fiber (NDF)], a low-fiber diet (LF; 29.6% NDF), and a high-fiber diet (HF; 34.8% NDF). The HF and LF diets were balanced to provide the same nutrient composition as the control diet when cows were fed a 7:3 ratio of HF:LF. Control cows were fed once daily at 0900h. Cows in the high/low treatment (H/L) were fed HF at 70% of daily offering at 0900h and LF at 30% of daily offering at 2200h; cows in the low/high (L/H) treatment were fed LF at 30% of daily offering at 0900h and HF at 70% of daily offering at 1300h. Dry matter intake was decreased 1.9kg/d by H/L compared with CON, but intake did not differ between H/L and L/H. The H/L and L/H treatments resulted in a large amount of feed consumed after each feeding, which shifted the daily patterns of starch and fiber intake. Treatments did not differ in total-tract digestibility. We detected no differences between CON and H/L for milk yield and composition. The H/L treatment unexpectedly tended to reduce milk and reduced milk fat yield compared with L/H, although L/H was expected to result in poorer rumen fermentation and decreased milk fat yield. Treatment did not affect milk fat concentrations of trans-10 C18:1, trans-11 C18:1, or de novo synthesized fatty acids, but H/L increased milk fat concentration of preformed fatty acids compared with CON (39.15 vs. 37.38% of FA, respectively). Treatment had no effect on plasma insulin or glucose at individual time points but did modify the phase and amplitude of the daily rhythms. Daily average plasma nonesterified fatty acids (NEFA) were decreased by H/L compared with CON and L/H, and H/L treatments decreased the amplitude of the daily rhythm of NEFA by 3.4 and 6.7µEq/L compared with CON and L/H, respectively. The amplitude of the daily rhythm of plasma blood urea N was increased by more than 15% by H/L compared with CON and L/H. Feeding multiple rations over the day changed the daily pattern of starch and fiber intake and decreased daily intake without decreasing milk yield or body weight gain over the 23-d observation periods. Feeding a high-fiber diet during the high-intake period of the day and a low-fiber diet during the low-intake overnight period failed to show other benefits, likely because of the change in feeding behavior.